Multiattack

The avatar makes three oozing tentacle attacks.

Oozing Tentacle

Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 31 (4d12 + 5) bludgeoning damage and 14 (4d6) acid damage.

Legendary Merge

A shoth with less than half its maximum hp can merge with any other shoth creature within 10 feet, adding its remaining hp to that creature's. The hp gained this way can exceed the normal maximum of that creature. The avatar can accept any number of such mergers.

Acid Wave (Recharge 5-6)

The avatar rises up and crashes down, releasing a 20-foot radius wave of acidic ooze. Each creature in the area must make a DC 20 Dexterity saving throw. On a failure, a creature takes 67 (15d8) acid damage and is knocked prone. On a success, a creature takes half the damage and isn't knocked prone.

Consult the Zom (1/Day)

The avatar uses its action to consult its weighty zom for insight. The zom flashes brilliant crimson-and-white light. Each creature within 120 feet who can see the avatar must succeed on a DC 20 Constitution saving throw or be blinded until the end of its next turn. Each creature of the avatar's choice within 120 feet that speaks a language must succeed on a DC 20 Charisma saving throw or be stunned until the end of its next turn as the avatar telepathically utters a short expression that is particularly meaningful to that creature.